Question

valence electrons of chlorine

Answer 1

This may be simpler
Chlorine has atomic number 17.
The atomic number is the number of protons present in the nucleus of an atom.All the atoms of an element have same atomic number.
In every stable atom the number of electrons is equal to the number of protons. Stable means that atom has not formed a ion yet.
Therefore, the number of electrons is equal to the number of protons in an chlorine atom.
This means, that the number of electrons present in an chlorine atom is 17.
The energy shells of an atom are in the order K, L, M …
So the electronic configuration of chlorine atom is: K, L, M = 2, 8, 7
Valence electrons are the number of electrons present in the outermost shell of an atom.
The last shell of a chlorine atom has 7 electrons in it.
This is helpful
This is confusing
Therefore, there are 7 valence electrons in an chlorine atom.

Answer 2

Chlorine is in the second last column of the pt, 8-1 =7